David is a 12-year-old sixth grader referred by his parents for evaluation. He currently resists going to school in the mornings due to his extreme and disabling anxiety. He also experiences severe headaches before leaving home. Socially, David has become increasingly isolated from his classmates and generally plays alone or with a neighbor who is two years younger than he is.

1. Based on the symptoms in the case study, what disorder(s) will be revealed in David's diagnosis. Please provide justification for your answer, and please feel free to reference the DSM-V.